When loading tanks of transport trucks it is necessary for a workman to open the hatch or hatches on the tank prior to loading and to close the hatches after loading. The surface of the tank is cylindrical and may be slippery which presents a hazardous condition for the workman. The hatch cover is normally hinged on a horizontal axis extending in the longitudinal direction of the tank and truck and when opened it is desirable to pivot the hatch cover to a fully open position in which the top of the cover rests on the upper part of one lateral side of the tank. If the side railing of a safety cage is spaced laterally outward a sufficient distance to permit the hatch cover to be fully opened, the side railing would be positioned too far laterally to prevent the worker from falling. It also may be too far away to be used by the worker as a grab bar to regain balance or to stop a fall.